Potty training puppy in an apartment building

Does anyone have tips on potty training a puppy in an apartment building? I have a 12 week old lab mix. She’s been doing pretty decent with not going in the apartment. She maybe will pee on the carpet once or twice a day, usually when she’s super excited playing. I think she knows that the apartment is not for peeing/pooping (only pooped in here once on her first night). However I can’t seem to get her to understand that the hallway/elevator/lobby are also “home” and not considered an appropriate place to pee. I’ve been carrying her out of the apartment til we get outside to make sure she won’t have accidents, but at the rate she’s growing that won’t be possible in a month or two. I give her treats and praise when she goes outside, but if I try to get her to walk down the hall, to the elevator, and out the lobby, there’s a good chance she’ll think it’s an OK time to pop a squat. How have others been able to train their dog to understand this?